Steroids have many accepted medicinal uses, among them being contraception and cancer chemotherapy. Much research has been devoted to the chemistry of the steroids, but very little is known about the details of the stereochemistry necessary to activate the steroid receptors. The proposal seeks funds to investigate the steroid-receptor interaction using a combination of synthesis and X-ray crystallography. The compounds to be studied are all generally linked to the reproductive process and are divided into three general categories: steroids with androgenic activity, cholesterol derivatives, and isoflavonoids with estrogenic activity. Our basic approach will be to determine the three dimensional structure for a series of compounds with known activity. From these results a hypothesis concerning the nature of the receptor interaction will be made. This hypothesis will be tested by the preparation of new compounds that should have a predictable activity.